Gas turbine engine fuel control



March 15, 1% W. H COWLES 3,240,015

GAS TURBINE ENGINE FUEL CONTROL Original Filed March 11, 1963 /7/MAX/MUM x50 OAS-RA 774 6 0 m ACCEL ERA 770/1/ aw pi) flTTOR/VEY UnitedStates Patent 3,240,015 GAS TURBINE ENGINE FUEL CONTROL Warren H.Cowles, Birmingham, Mich, assignor to Hoiiey Carburetor Company, Warren,Mich, a corporation of Michigan Original appiication Mar. 11, 1963, Ser.No. 264,117. Divided and this application Nov. 19, 1964, Ser. No.412,437

12 Claims. (Cl. 6039.28)

This application is a divisional of application Serial No. 264,117,filed on March 11, 1963, in the name of Warren H. Cowles, now abandoned.

This invention relates generally to fuel controls, and more particularlyto closed-loop scheduling types of fuel controls for gas turbineengines.

It is well known that parameters of pressure, speed, and, if necessary,temperature may be used independently and/ or collectively forcontrolling and determining the operation of gas turbine power plants.However, the means heretofore employed to sense these various parametersand to provide corresponding input signals or control forces havegenerally been rather complex, often involving squared factors.

This invention embodies a fuel valve design that eliminates having tocope with squared flow factors resulting from the restriction or orificetype flow usually employed in gas turbine engine fuel controls. Theinvention also embodies a novel direct coupling between the pneumaticpressure sensor and the bypass valve, producing various advantages overpreviously known systems.

Another object of the invention is to provide such a system wherein thereaction time or response to changes in the selected pneumatic pressureis immediate and, hence, much faster than in prior systems, due to theabove mentioned direct coupling technique.

It is a further object of the invention to provide a fuel control devicehaving a novel high pressure acceleration fuel system, wherein highpressure moving seals may be avoided and low pressure seals used in lieuthereof between the fuel and pneumatic chambers.

Other objects and advantages of the invention will become apparent whenreference is made to the following specification and the accompanyingdrawings wherein:

FIGURE 1 is a schematic illustration of a gas turbine engine havingconnected thereto a fuel control constructed in accordance with theinvention;

FIGURE 2 is a cross-sectional view of a complete fuel control embodyingthe invention;

FIGURE 3 is a graph illustrated generally the relationships of fuel flowto engine speed for engine operating conditions such as acceleration,steady state, and decelera tion;

FIGURE 4 is a graph illustrating generally the relationship of fuel flowto pressure drop as would result in this system as compared to priorsystems; I

FIGURE 5 is a graph illustrating a characteristic of a fuel controlembodying the invention.

Referring now in greater detail to the drawings, FIG- URE 1 illustratesschematically a gas turbine engine having a fuel control 12 which isresponsive to manual control by means of a selector lever 14, to enginespeed by means of a gear box 16 and transmission line 18, and tocompressor discharge pressure via a pressure probe 20 and conduit 22.

While the fuel control 12 shown and to be described herein is responsiveto particular parameters, it should be understood that certain novelfeatures of the invention may be employed in a fuel control responsiveto other parameters, such as temperature and engine pressures other thanthat specified herein. A's to those features, no

ice

limitations are intended by the particular parameters employed in thepresent disclosure for purposes of illustration.

A typical gas turbine engine 10 includes an outer housing 24 with anintake 26 and exhaust nozzle 28. A combustion chamber 30 having a fueldistribution ring 32 therein is located within the housing 24 betweenthe compressor 34 and turbine 36.

The fuel supply system generally comprises a fuel tank 38, an enginedriven pump 40, and supply conduits 42 and 44 which deliver fuel to thefuel control 12. The fuel control 12 meters the correct fuel flow forthe particular engine operating requirements, as dictated by the abovementioned engine speed and compressor discharge pressure parameters in amanner which will be described below. Correctly metered fuel istransferred to the fuel distribution ring 32 via a conduit 46, anyexcess fuel being by-passed back to the inlet side of the pump 40 via areturn conduit 48, in a manner to be described.

As seen in FIGURE 2, the fuel control 12 comprises a plural cavityhousing 50 formed in any suitable manner and containing an all-speedisochronous type governor system 52, an acceleration fuel system 54, afuel reset device 56 and a speed bias device 58, the latter two devicesbeing optional additives. The acceleration fuel system 54 includes aforce balance system 60 operative in conjunction with a linearrestrictor valve 62. These various components will now be described indetail.

Acceleration fuel system A force balance lever 64 is pivotally securedto the fuel control housing in one of the chambers 66 therein. A valvestem 68 is pivotally connected to the lever arm 64, at a predetermineddistance L from the pivot point 69 of the lever 64, so as to bepositioned substantially perpendicular to the arm 64. The ends of thevalve stem 68 may, of course, be slidably confined within guide members(not shown). Two reduced diameter portions 70 and 72 formed on the stem68 cooperate with a pair of annular openings or valve seats 74 and 76formed within the housing 50 to function as a pair of valves. Outletconduits 78 and 80 communicate with the openings '74 and 76,respectively, and converge into the single conduit 48 which returns tothe inlet side of the pump 40.

An evacuated bellows 82 in another chamber 84 of the housing 50 isfixedly attached at its one end to a wall 86 of the housing 50, theother end thereof being secured to an extension 88 of the valve stem 68for movement therewith. Compressor discharge air enters the chamber 84via the conduit 22, and the pressure in chamber 84 is referenced toabsolute zero by virtue of the bellows 82 being evacuated. A lowpressure seal, which may be a diaphragm 5 0, is sufficient to separatethe return line 80 from the air chamber 84.

A third chamber 92 is formed by sealing a recess formed in the wall ofchamber 66 with a diaphragm 94. A washer 96 fastened in the usual mannerto the diaphragm 94 serves as a seat for one end of a spring. 98, theother end thereof seating against a wall 100 of the housing 50. A stem102 extends from the washer 96 into the chamber 66 and is pivotallyattached to the lever arm 64 at a second predetermined distance L fromthe fixed pivot point 69.

A so-called linear restrictor valve 62 is located within still anotherchamber 104 formed within the housing 50. This valve 62 may slide alonga fixed guide member 106 and be urged toward the valve seat 108 by thespring 110. A conduit 112 communicates between the chamber 104 and thechamber 92. The previously mentioned conduit 46, leading to the fueldistribution ring 32, communicates with chamber 104 of the fuel controlunit 12 by way of the passage 47.

The fuel line 44 from the pump 48 enters the fuel control housing 50 atan inlet port 114. The chamber 116 contains a valve 118 urged toward theseat 128 by the spring 122. A passage 124 communicates between the inletport 114 and the chamber 116. A passageway 126 communicates between thechamber 116 and the chamber 66.

Governing system The transmission line 18( FIGURE 1) is connectedbetween a gear box 16 driven by the engine shaft and the shaft 128extending from the fuel control housing 58. As seen in FIGURE 2, ahydraulic speed sensing unit 130 of a conventional centrifugal type isattached to the shaft 128 for rotation therewith. The speed sensing unit130 may be substantially comprised of a generally tubular center portion132 which has formed thereon or secured thereto a pair of radiallyextending members 134 and 136. The member 136 has an axial borecontaining a centrifugal valve 138 which is normally urged open by thespring 140. The valve 138 is thus adapted to control fluid flow throughport 142 which is formed within the member 136 in accordance with thespeed of the engine 10.

A spring 144 and spring seat 146 located in a chamber 148 maintain aproper location of the members 134 and 136 within the generallycylindrical chamber 150, as the members 134 and 136 are rotated by theshaft 128 and transmission 18. A seal 152 prevents leakage or flowbetween the chambers 148 and 150, other than through passage 141 in thevalve weight and the port 142. A conduit 154 containing a restriction156 communicates between the conduit 124 and the chamber 150, while thevalve 138 and chamber 148 serve to communicate between the chamber 156and a passage 158 leading from the passage 126.

The valve 118 is provided to maintain a constant pressure drop acrossthe port 142 resulting from How changes other than those due to movementof the valve 138 in response to engine speed.

The fuel control uni-t 12 contains another chamber 168 providingcommunication between conduits 158 and 162. A diaphragm 164 forms amovable wall between the chamber 160 and still another chamber 166, anda conduit 168 communicates between the chambers 166 and 150. A member170 extends from the diaphragm washer 172 into the chamber 160 so as tocontact the lever arm 173, the latter being pivotally supported at itsone end on a pivot pin 174 secured to wall 176 of the housing 56. Thelever arm 173 includes a valving surface 178 adapted to engage the valveseat 180 at the inlet to the conduit 162. The movable spring seat 188 isslidably mounted in the cylinder 189 formed in the housing 50 forreciprocal actuation therein in response to the position of therotatable cam 190 connected to the manual selector lever 14 (FIGURE 1).An adjustable minimum fuel flow stop 192 extends into the chamber 168 soas to limit the counter-clockwise movement of the lever arm 173.

Fuel reset device When one is desired, a so-called fuel reset device 56may be provided by forming a chamber 194, a conduit 196 communicatingbetween conduit 162 and chamber 194, and a diaphragm 198 forming amovable wall between chamber 194 and another chamber 280. A passage 201communicates between chamber 280 and the linear restrictor valve chamber104. A stem 202 attached to the diaphragm washer 204 extends across thechamber 200 and into chamber 160. A spring seat 206 formed to receivethe end of the stem 202 supports one end of spring 208, which urges thelever arm 173 in a clockwise direction so as to move the valving surface1'78 away from the valve seat 180.

Speed bias device When required by a particular engine, the speed biasdevice 58 may be provided by forming a chamber 210, a conduit 212communicating between chamber 210 and conduit 168, and a diaphragm 214forming a movable wall between the chamber 210 and chamber 66. A spring216 is confined between the diaphragm washer 218 and a spring seatmember 220 so as to urge the diaphragm 214 away from the chamber 66toward an adjustable stop 222 extending into chamber 210.

A stem 230 extends from the diaphragm washer 218 and into the chamber66, along the axis of spring 216. A leaf spring 226, fixedly mounted atits one end 228 on a wall of the housing 50, is attached at a point 230intermediate the ends thereof to the end of the stem 224. The free end232 of the leaf spring 226 at times contacts the free end 234 of thelever arm 64 to retard movement of the latter for a purpose to bedescribed later. A second adjustable stop 236 serves to limit themovement of the leaf spring 226 against the lever arm 64.

Operation Before explaining the operation of the fuel control 12 indetail, it is deemed advisable to first give a brief summary of itsoperation. As explained above, fuel from the tank 38 is supplied to theinlet 114 of the fuel control 12 by means of pump 40, which is usually(but not necessarily) driven by the engine and the capacity of which ismore than suflicient to supply the total fuel requirement under anyoperating condition of the engine. The amount of fuel actually suppliedto the engine is, of course, determined by the fuel control itself. Fromthe inlet 114, fuel flows past valve 118, through passage 158, intochamber 160, past valve 178 and through the orifice 18%), throughpassage 162, past valve 62, through passage 47 and then to the enginethrough conduit 46. It will thus be seen that all of the inlet fuel goesto the engine, except that fuel which is by-passed through passage 126,chamber 66, orifices 74 and 76, passages 78 and and back to the inlet ofthe pump 40 through conduit 48.

The fuel supplied to the engine is controlled by the valve 178, inresponse to the movement of throttle 14 which rotates the cam 190 toload spring 184. The load on spring 184 is modulated by a pressuredifferential generated by the speed sense mechanism and applied todiaphragm 164 and by the pressure differential across valve 62, thelatter differential being an indication of instantaneous fuel fiow andapplied across diaphragm 198 so as to be resiliently transmitted tolever 173 by spring 208.

Inlet fuel which is not supplied to the engine but returned to the pump40 is by-passed through orifices 74 and '76 controlled by valve member68 according to a balance of moments about pivot 69. The primary balanceis between the compressor discharge pressure acting on evacuated bellows82 in opposition to the pressure differential between chamber 66 andoutlet passage 47 applied to diaphragm 94, the balance being shiftedbetween limit stops 222 and 236 by the pressure differential generatedby the speed sense mechanism 130 acting across diaphragm 214 andresiliently applied to the lever 64 through the leaf spring 226,

It may also be advantageous to first describe generally the operation ofthe basic closed-loop moment balance system 60 and the effect of thenovel linear restrictor valve 62. For this purpose, it can be assumedthat the system 60 is in equilibrium and that the compressor dischargepressure decreases for some reason or other that is not important inthis discussion. With that assumption in mind and referring to FIGURE 2,it can be seen that as the valve stem 68 and the attached lever am 64move to the left in response to a decrease in compressor dischargepressure surrounding the evacuated bellows 12, more fuel is by-passedthrough the ports 74 and 76, passages 78 and 80 and ultimately to theinlet of the pump 40 through the conduit 48. This results in a decreasein pressure in the chamber 66 and in the conduits 126, 158 and 162, aswell as a reduced fuel flow to the engine. The linear restrictor valve62 is then urged toward a more nearly closed position by the spring 110,resulting in a decrease in pressure in conduit 112 and the chamber 92 tothe left of the diaphragm 94.

Ignoring for the moment the governing system valve 178/180 andconsidering pressure P in chamber 161) to be substantially the same aspressure P in passage 162, it can be seen from the solid straight linecurve of FIG- URE 4 that the pressure differential P P will decreaselineally as fuel flow W, decreases. This linear relationship is achievedby suitably contouring valve 62. Since the force F was reduced due tothe decrease in compressor discharge pressure, the reduced P -Pdifferential, which produces a lesser force F than before the additionalfuel was by-passed, and the constant force of the calibrated spring 88results in a return of the moment balance system back to equilibrium. Inother words, a reduction in force F eventually results in a reduction inforce F so as to return the system to equilibrium. The term closed-loopis commonly applied to this type of equilibrium seeking moment balancesystem, and the above type of operation takes place whenever anythingoccurs to throw the system out of balance.

If a fixed restriction were employed in lieu of the linear restrictionvalve 62, as has been the common practice heretofore, equilibrium couldstill be obtained; however, a much more complicated system ofdiaphragrns, levers, and/or springs would be required for use inconjunction with the acceleration fuel lever 64, as will become moreapparent later in the description.

The detailed operation of the fuel control unit 12 will now be discussedin conjunction with a typical fuel flow (W vs. speed (N) curve (FIGURE3) illustrating the various engine operating conditions, without regard,at this point, to the optional fuel reset device 56 and speed biasdevice 58.

It will first be assumed that the engine 18, and consequently the pump48, has been started and that the fuel control unit 12 is receivingfuel, at a pressure P from the pump 40 through the inlet port 114. Forpurposes of illustration, the engine idle operating conditions arerepresented by point A of FIGURE 3. At this time, the pressures withinthe fuel control unit 12 would be as indicated by FIGURE 2, i.e., therewould be a pressure drop across the valve 118 resulting in a pressure Pin the chamber 116, the conduit 126, and the chamber 66. There would bea further pressure drop across the valve seat 178/ 180 producing P inthe conduit 162. An additional pressure drop would take place across thevalve 62, resulting in fuel at a pressure P supplied to the engine 18,as well as in the conduit 112 and the chamber 92.

Under the above circumstances, the system would be in a steady state orequilibrium condition; that is, the compressor discharge pressure,hereinafter referred to as CDP, would have compressed the evacuatedbellows 82 resulting in a force F to the right (FIGURE 2) so as toproduce a moment balance about the lever arm 64 of the force F resultingfrom the P P relationship in the chambers 66 and 92, less the force ofthe spring 98. As illustrated in FIGURE 2, L and L may be anypredetermined lengths along the lever arm 64.

A particular amount of fuel would now be by-passed, through the conduits78, 80 and 48, back to the pump- 40 inlet.

.Prior to take-off, the manual selector lever 14 would be pivoted so asto rotate the cam 190 in a counterclockwise direction until some point Xis in contact with the spring seat 188. Looking again at FIGURE 3, theresult of moving lever 14 would be an acceleration, which is a 6transient or non-equilibrium condition, along the dotted curve towardsome equilibrium or steady state point B on the sea level curve. Duringthis transient condition, the spring seat 188 would have been moveddownwardly, compressing the spring 184 and instantaneously rotating thelever arm 173 and its valving surface 178 completely away from the valveseat 188 to some maximum stop, the stop being determined either by thelimit of movement of stem 170 downwardly against the pressure P or bysome definite fixed stop similar to stop 192. Since the pressure F fromthe pump 40 would increase with the increasing speed, P would now behigher, and, with the lever arm 173 away from the seat 180, P would besubstantially equal to P allowing more fuel to flow past the linearrestrictor valve 62 and to the engine 10. At the same time, R; wouldhave increased in the chamber 1104, conduit 112 and the chamber 92.However, because of the contoured shape of the valve 62 and asillustrated by FIGURE 4, a higher pressure differential P P would haveresulted across the diaphragm 94, thereby overcoming the spring 98 tomove the lever arm 64 to the left in FIGURE 2. The valve 68 would thusmove toward a more open position so as to bypass more fuel through theconduits 78, 8t) and 48. In the meantime, however, CDP would haveincreased in the chamber 84, thereby tending to compress the evacuatedbellows 82 and restrict the bypass flow through the ports 74 and 76.

As the speed increases, pressure P would likewise have been increased,as would the P P differential originally established by the valve 118.This would move the diaphragm 164 and stem 178 upwardly, therebypositioning the valving surface 178 of the lever arm 173 closer to theseat 180, until such time as the upward movement of lever 173 iscounteracted by the force of the spring 184 on the lever arm 173. Thiswould throttle or reduce the fuel flow from the chamber 168 into theconduit 162 and, in turn, reduce P in the chambers 184 and 92. Becauseof the actuation of the valve 178/ 180, and as a result of the decreasedflow W past the valve 62, the pressure differential P P across thediaphragm 94 would once again have decreased, on a line somewherebetween the solid and dotted lines of FIGURE 4. This and the force ofthe spring 98 would move the diaphragm 94, and hence the lever arm 64,toward the right in FIGURE 2. The valve stem 68, being affixed to thelever arm 64, would also move to the right, until balanced by the effectof CDP on the evacuated bellows 82. Since the above operation is at sealevel, the resultant balanced condition would be represented by point Bon the sea level curve of FIG- URE 3.

Once the aircraft has taken off and while climbing to some altitudewhich is represented by point C in FIGURE 3, GDP will continuallydecrease, permitting the valve stem 68 to move toward the left in FIGURE2. This will by-pass more fuel through the conduits 78, and 48 and tothe pump 40 inlet, causing a reduction of pressure P in chamber 66,conduits 126 and 158 and the chamber 160. P would decrease, permittingthe spring to force the linear restrictor valve 62 toward the seat 108,thereby reducing the flow through the conduit 46 to the engine 18, andat the same time reducing pressure P in the chambers 104 and 92. The 1-1 differential would, of course, be lowered with decreased fuel flow,permitting the acceleration fuel system 54 to once again come to anequilibrium condition.

Steady state or equilibrium operation represented by point C in FIGURE 4would be maintained until such time, for example, as it would be desiredto decrease speed. Decreasing speed would be accomplished by movingselector lever 14 in the opposite direction so as to rotate camclockwise from X to Y, thereby lowering the pressures throughout thesystem, increasing by-pass fuel flow and decreasing fuel flow to theengine, all of which is the reverse of what happened when cam 190 wasfirst moved to X. The above would result in a deceleration from point Cto point D, along the dot-dash line of FIGURE 3, the precisedeceleration line being determined by the setting of the minimum flowstop 192.

Acceleration from point D to a greater speed at a different altitude,such as indicated by point E, would be along the dash-double dot line tothe dotted acceleration line, and then along the dotted line past B toE.

From the above description, it will be apparent that a fuel controlembodying the invention is adapted for use with any gas turbine enginehaving operating conditions typically represented by curves such asthose shown by FIGURE 3.

While the over-all operation described above is very generally similarfor many prior fuel control systems, the invention embodies certainspecific novel features which produce a much quicker, less cumbersomeand more accurate response than is generally obtained. For example,since the linear restrictor valve 62 is deliberately contoured so thatthe area defined by seat 108 varies directly with the square root of thepressure drop, the linear relationship referred to above (see FIGURE 4)between metered fuel flow and the pressure drop P P across the valve 62is produced. This is in contrast with conventional flow throughrestrictions commonly used in prior art fuel controls and resulting in apressure drop which is proportional to the square of the fluid flowtherethrough. For example, the change in pressure across an orifice maybe proportional to (WM-(1) or W +2qW +q wherein q is simply computerfuel used for hydraulic multiplication and returned to the pump. Becausethe flow through the usual orifice or restriction is non-linear, asillustrated by the dotted line curve of FIGURE 4, prior art fuel controldevices require a more complicated system of diaphragms, levers and/ orsprings to be used in the acceleration system lever or other structurein order to cancel out the squared factors (W and q and leave only W; asthe fuel flow to the engine.

Another novel feature incorporated in the above described accelerationfuel system 54 is the direct connection between the by-pass valve 68 andthe pneumatic pressure sense 82. This produces an immediate response toGDP changes, as opposed to the usual. indirect linkages and conduitrysystems prevalent in the heretofore known fuel control units.Additionally, since the bypass valve 68 drops the pressure from the highpressure P to pump inlet pressure, a simple low pressure seal, such asthe movable diaphragm 90, may be used between the fuel passage 80 andthe air in the chamber 84. Thus, the usual high pressure seal requiredin prior art devices is avoided. The result is a greatly improvedoperation because bellows 82 is free to operate quickly and accurately,there being no friction load on stem 88.

Fuel reset device 56 is incorporated in the governing system 52 whenisochronous governing characteristics are desired. Referring again toFIGURE 2, it can be seen that the pressure above the diaphragm 198 inthe chamber 194 is always greater than that below the diaphragm 198 inthe chamber 260 due to the pressure drop across the valve 62. It is thusapparent that the fuel flow to the engine at a given speed, would begreater with a fuel reset device 56 in the system than would be the casewithout such a device, since the valving surface 178 of the lever arm172 would be maintained farther away from the seat 180. The practicaleffect of this fuel reset device 56 is isochronous governing,represented by the X-line in FIGURE 3 leading from the accelerationcurve to some point, such as C; Without device 56, governing would besuch as that indicated by the shallower dotted line leading to point Cthrough points B and E. The ease with which this effect is accomplishedis greatly facilitated by the controlled pressure drop across the linearrestrictor valve 62.

One gas turbine engine specification sometimes re quired to beconsidered is, in effect, a plot of W /CDP vs. N (speed). Some engines,for example, require a constant W /CDP ratio over the entire speedrange; other engines require a varying ratio such as that shown inFIGURE 5 wherein the ratio is greater at higher speeds.

The function of the speed bias device 58, which may be added to theacceleration fuel system 54 when desired, is to provide the effect shownin FIGURE 5. Whether the effect of device 58 is to be applied to theforce balance system 60 over the complete speed range or some portionthereof may be controlled by changing the preload of spring 216 and/ orby adjusting the stops 222 and 236.

From FIGURE 2, it can be seen that the pressure differential P '-P willincrease as the speed sensor valve 138 closes with increasing speed.Since this same pressure differential is applied across diaphragm 214,it is evident that the effect of the increased Pf-P is to move thediaphragm 214- to the right in FIGURE 2 so as to increase the force ofleaf spring 226 acting on the end 234 of the lever 64. Even though GDPis continually increasing with increased speed, the increased force ofthe leaf spring 226 on the lever 64 provides the same effect as if CDPwere increasing at some greater rate, so as to move valve 68 farther tothe right and reduce the amount of fuel by-passed through ports 74 and76, passages 78 and 80 and conduit 48. This increases the fuel flow tothe engine, W accordingly. The above effect is illustrated by the lineF-G in FIGURE 5.

It is apparent that a constant W /CDP ratio would be maintained, despiteincreased speed, any time that the stem 224 to which the leaf spring 226is fixed engages the adjustable stop 236. This is represented by theline G-J, FIGURE 5. Similarly, a constant W /CDP ratio would bemaintained at lower speeds, line HF of FIGURE 5, so long as Pf-P is lowenough so that the leaf spring 226 does not exert a force on the leverarm 64.

From the above discussion, it is apparent that the invention provides acompact and efficient fuel control device having a number of novelfeatures resulting in greater accuracy, faster response and fewer partsas compared to prior art devices. It should also be apparent that theuse of the device disclosed herein is not limited to aircraft gasturbine engines.

It should be further apparent that the invention provides a novel directconnection means between the usual pneumatic pressure sensor and theacceleration fuel system lever arm, with the connector serving as aby-pass valve and operating in such a manner that an immediate responseto the selected pressure results. This produces a considerable advantageover the indirect linkage and complicated conduitry systems which havebeen prevalent in previously known fuel control systems.

Although but one embodiment of the invention has been disclosed anddescribed, it is apparent that other modifications may be made withinthe scope of the appended claims.

What I claim as my invention is:

I. A fuel control mechanism for a gas turbine engine including acompressor, said fuel control mechanism comprising a source of fuelunder pressure, an inlet port for said fuel; an outlet port; a conduitcommunicating therebetween; first valve means in said conduit operableto control fuel flow; and a closed-loop moment balance system forregulating the flow through said conduit, said system including a leverand a bypass valve means, said bypass valve means including a valve, avalve stem, a second outlet from said conduit, and a passagewaycommunicating between said second outlet and said source of fuel, saidstem being pivotally connected to said lever at substantially rightangles thereto, a first device responsive to a selected compressorpressure and fixedly attached to said valve stem, and a second deviceresponsive to the difference in fuel pressure across said first valvemeans and pivotally connected to a second point along said lever.

2. A fuel control mechanism for a gas turbine engine including acompressor, said fuel control mechanism comprising a source of fuelunder pressure, an inlet port for said fuel; first and second outletports; separate conduits communicating between said inlet port and eachof said outlet ports; first valve means in said conduit leading fromsaid inlet port to said first outlet port; and a closed-loopacceleration fuel system for regulating the flow through said conduits,said system including a lever and bypass valve in said conduit leadingfrom said inlet port to said second outlet port, said bypass valveincluding a stem having a contour formed thereon for coaction with saidsecond outlet port, said stem being pivotally connected to said lever atsubstantially right angles thereto, a first device responsive to aselected compressor pressure and fixedly attached to said stem, and asecond device responsive to the difference in fuel pressure across saidfirst valve means and pivotally connected to a second point along saidlever, said second pressure responsive device forming a movable wallbetween the fluid in said second conduit and the fluid in said firstconduit downstream of said valve means.

3. In combination with the device described in claim 2, a governorsystem having a second valve means in said conduit leading from saidinlet port to said first outlet port.

4. A device as described in claim 3, and including additionally a thirdpressure responsive device for at times influencing said second valvemeans, said device being responsive to the difference in fuel pressureacross said first mentioned valve means.

5. A fuel control mechanism, comprising a housing; a source of fuelunder pressure; a fuel inlet port; a source of air under pressure; afuel outlet port; a fuel bypass port; an air inlet port; a firstpassageway communicating between said fuel inlet port and said fueloutlet port; a second passageway communicating between said fuel inletport and said fuel bypass port; and an acceleration fuel system forinfluencing the amount of flow through said outlet and said bypassports, said acceleration fuel system including first valve means in saidfirst passageway, second valve means in said second passageway, saidsecond valve means including a valve and a valve stem, said valve stemcooperating with said fuel bypass port, the movement of said valve andvalve stem being responsive to the pneumatic pressure entering saidhousing through said air inlet, a lever arm pivotally connected to saidstem at a point intermediate the ends thereof and pivotally connected atone of said ends to said housing, and a device responsive to thedifference in fuel pressure across said first valve means and pivotallyconnected to said lever substantially near the other end thereof.

6. In a fuel control for a gas turbine engine including a compressor,said fuel control having a housing, a source of fuel under pressure, aninlet port for said fuel, an outlet port, and a closed-loopcommunication system including a main fuel passage therebetween, anacceleration fuel system for regulating the flow through said main fuelpassage, said acceleration fuel system comprising a moment balancesystem including valve means for bypassing fuel, said valve meansincluding a valve stem, a valve formed thereon, an opening operativelyconnected to said main fuel passage and a conduit communicating betweensaid opening and said source of fuel, a lever pivotally connected at itsone end to said housing and being operably connected to said valve stemat a point intermediate the ends thereof, a first device responsive to aselected compressor pressure and fixedly attached to one end of saidvalve stem, a second valve means in said main fuel passage formaintaining a linear relation between metered fuel fiow and pressuredrop thereacross, a second pressure responsive device operably connectedsubstantially near the other end of said lever, and a conduitcommunicating between said second pressure re sponsive device and apoint intermediate said second valve means and said outlet port.

'7. A fuel control system for a gas turbine engine includ ing acompressor, said fuel control system comprising a housing, a source offuel under pressure, an inlet port for said fuel, an outlet port, aconduit communicating therebetween, a first chamber in communicationwith said conduit, a lever and bypass valve means in said first chamher,said bypass valve means including a stem, a valve formed thereon, anopening in said chamber adjacent said valve and a passage communicatingbetween said opening and said source of fuel, said lever being pivotallysupported at its one end in said housing and being operably connected tosaid stem at a fixed distance from said pivotally supported end, asecond chamber containing a device responsive to a selected compressorpressure, said pressure responsive device being fixedly attached to saidstem, seal means between said first and second chambers surrounding apart of said stem, second valve means in said conduit for maintaining alinear relation between metered fuel flow and pressure drop across saidsecond valve means, and a second pressure responsive device operablyconnected to said lever at a second fixed distance from said pivotallysupported end, said second device being operatively connected to saidsecond valve means so as to be responsive to the difference in fuelpressure across said second valve means and forming a movable wallbetween said first chamber and a third chamber.

8. An acceleration fuel system comprising a source of fuel underpressure, an inlet port for said fuel; an outlet port; a closed-loopcommunication system including a main fuel passage therebetween, saidclosed-loop communication system including a source of air underpressure, a valve means for bypassing fuel, said valve means including astem having reduced diameter portions formed at two points thereon and apair of coacting valve seats, a lever pivotally supported at its one endand being pivotally connected to said stern fixed distance from saidpivotally supported end so as to be movable therewith, a first deviceresponsive to said air pressure and fixedly attached to one end of saidstem, and a second pressure responsive device operably connected to saidlever at a second fixed distance from said pivotally supported end; alinear restrictor valve in said main fuel passage for maintaining alinear relation between metered fuel flow and pressure drop across saidrestrictor valve; and a means of communication between said secondpressure responsive device and a point intermediate said linearrestrictor valve and said outlet port.

9. In a fuel control for a gas turbine engine, including a housing and afuel passage therethrough, a source of fuel under pressure, anacceleration fuel system for regulating the flow through said passage,said system comprising a first chamber in said housing, a lever arm insaid first chamber pivotally attached at its one end to said housing, asource of air under pressure, a second chamber in said housing forreceiving said air, a device in said second chamber fixedly attached atits one end to said housing and being responsive to said air pressure, abypass valve means pivotally attached to said lever arm, said bypassvalve means including a stem having reduced diameter portions formed onthe ends thereof for coaction with a pair of seats, said seatssurrounding two outlets from said first chamber, one of said ends beingfixedly attached to said pressure responsive device, a second pressureresponsive device pivotally atached to said lever arm substantially nearthe other end thereof, said second pressure responsive device forming amovable wall between said first chamber and a third chamber, a firstresilient means located in said third chamber for urging said secondpressure responsive means toward the first chamber, a second valve meansin said fuel passage for maintaining a linear relationship betweenmetered flow through said passage and the pressure drop across saidsecond valve means, said second valve means including a contoured valve,a valve seat formed in said fuel passage and a second resilient meansfor urging said contoured valve toward said valve seat against the forceof the fluid flow therethrough, and a conduit communicating between saidthird chamber and said fuel passage downstream of said second valvemeans, said second pressure responsive device being respo-nsive to thedifference in fuel pressure across said second valve means.

10. In a fuel control mechanism for a gas turbine engine including acompressor, said fuel control mechanism having a source of fuel underpressure, an inlet port for said fuel, an outlet port, a passagewaycommunicating therebetween and fuel metering means in said passageway, aclosed-loop moment balance system for regulating the fiow through saidpassageway, said system comprising first means responsive to a selectedcompressor pressure and second means pivotally connected to said firstmeans for bypassing variable amounts of said fuel back to said source inresponse to movement of said first means, said second means including apair of openings formed in said passageway upstream of said fuelmetering means, a valve stem pivotally connected to said first means, apair of reduced diameter portions formed on said valve stem, and aconduitry system communicating between said openings and said source offuel.

11. In a fuel control mechanism for a gas turbine engine including acompressor, said fuel control mechanism having a source of fuel underpressure, an inlet port for said fuel, an outlet port, a passagewaycommunicating therebetween and fuel metering means in said passageway, aclosed-loop moment balance system for regulating the flow through saidpassageway, said system comprising first means responsive to a selectedcompressor pressure, second means responsive to the pressuredifferential across said fuel metering means, and third means operablyconnected to said first and second means for variably bypassing saidfuel back to said source in response to movement of said first andsecond means, said third means including a stem having a pair of reduceddiameter portions formed thereon, a pair of openings formed in saidpassageway for cooperation with said reduced diameter portions, and aconduitry system comunicating between said openings and said source offuel.

12. A fuel control mechanism, comprising a housing; a source of fuelunder pressure; a fuel inlet port; a source of air under pressure; afuel outlet port; a fuel bypass port; an air inlet port; a firstpassageway communicating between said fuel inlet port and said fueloutlet port; a second passageway communicating between said fuel inletport and said fuel bypass port; and an acceleration fuel system forinfluencing the amount of fiow through said outlet and said bypassports, said acceleration fuel system including first valve means in saidfirst passageway, second valve means in said second passageway, saidsecond valve means including a valve and a valve stem, said valve stemcooperating with said fuel bypass port, the movement of said valve andvalve stem being responsive to the pneumatic pressure entering saidhousing through said air inlet, a lever arm pivotally connected to saidstem at a point intermediate the ends thereof and pivotally connected atone of said ends to said housing, a pressure responsive device pivotallyconnected to said lever substantially near the other end thereof and aconduit communcating between said pressure responsive device and saidfirst passageway downstream of said valve means.

References Cited by the Examiner UNITED STATES PATENTS 2,636,553 4/1953Ballantyne. 2,871,659 2/ 1959 Chamberlin. 2,943,447 7/1960 Davies.3,068,648 12/ 1962 Fleming. 3,073,329 1/1963 Kast -3928 X 3,076,3102/1963 Gayfer 6039.28 3,078,669 2/1963 Williams 6039.28 3,118,491 1/1964Simons 60-3928 X JULIUS E. WEST, Primary Examiner.

MARK NEWMAN, Examiner.

1. A FUEL CONTROL MECHANISM FOR A AS TURBINE ENGINE INCLUDING ACOMPRESSOR, SAID FUEL CONTROL MECHANISM COMPRISING A SOURCE OF FUELUNDER PRESSURE, AN INLET PORT FOR SAID FUEL; AN OUTLET PORT; A CONDUITCOMMUNICATING THEREBETWEEN; FIRST VALVE MEANS IN SAID CONDUIT OPERABLETO CONTROL FUEL FLOW; AND A CLOSED-LOOP MOMENT BALANCE SYSTEM FORREGULATING THE FLOW THROUGH SAID CONDUIT, SAID SYSTEM INCLUDING A LEVERAND A BYPASS VALVE MEANS, SAID BYPASS VALVE MEANS INCLUDING A VALVE, AVALVE STEM, A SECOND OUTLET FROM SAID CONDUIT, AND A PASSAGEWAYCOMMUNICATING BETWEEN SAID SECOND OUTLET AND SAID SOURCE OF FUEL, SAIDSTEM BEING PIVOTALLY CONNECTED TO SAID LEVER AT SUBSTANTIALLY RIGHTANGLES THERETO, A FIRST DEVICE RESPONSIVE TO A SELECTED COMPRESSORPRESSURE AND FIXEDLY ATTACHED TO SAID VALVE STEM, A SECOND DEVICERESPONSIVE TO THE DIFFERENCE IN FUEL PRESSURE ACROSS SAID FIRST VALVEMEANS AND PIVOTALLY CONNECTED TO A SECOND POINT ALONG SAID LEVER.